Ratio rockers & double springs - seat pressure and bind issues?

[petew]

Hi all,

Got my 1600 turbo street motor in with the engine builder having a few things sorted. At the same time, I've upgraded to double valve springs and 1.25:1 ratio rocker for a little more breathing. It's running stock valves and stock heads with an Engle TCS-10 turbo cam.

http://rodpenroseracing.com.au/springs/ ... mance.html
http://rodpenroseracing.com.au/rocker-k ... s-kit.html

The heads are machined and it's going together but... My engine builder (highly experienced) is having real concerns about 2 things;

1. The seat pressure is 170lbs. He's worried it's too high.
2. The ratio rockers are lifting 490 (intake)/479 (exhaust) which is leaving him with only 60 thou before binding at full lift.

He's specifically concerned that given a missed gear shift or the like, something has to give. Ie. we'd end up popping a valve or recession in the head. Like to hear people's thoughts on this.

Cheers.

[Marc]

Which springs are you using? If they're the Engle 6602, they're rated at 125 lbs @1.600" installed height (and 280 lbs @ .550" lift). Is your installed height significantly less, and could it be increased by using thinner shims and/or different retainers?
170 lbs seat pressure isn't obscenely high but I think it's more than you should need.
.060" from coil bind is frightening to me too...although it's within the .050"-.075" that Gene Berg recommended for race engines - with the caveat that spring life will be reduced and you'll need to accept some breakage
For a street engine I'd want ~.150" from coil bind at full lift.
Hopefully you can find some "thinner" retainers that'll increase the installed height ~.100" without having a clearance problem at the rockerarms; otherwise I'd be shopping for some different springs.

Opinions/experiences will vary but that's my 2¢ worth.

[petew]

They're the scat springs in the link above.

[Marc]

Oh, are they the #20179? I was confused by the photo, which shows single springs.
I don't have a Scat catalog anymore and the only one I found online doesn't give specs for the springs in that kit -
But if the springs are the #20085, they're supposed to be 175 lbs at 1.550".

Elsewhere I found the free length given as 2.400" outer, 2.025" inner FWIW in identifying them.

#20085 are supposed to coil bind at .900", so at an installed height of 1.550" and .490" lift you should have .160" to go before coil bind - right now it looks as though your installed height must be about 1.450".

So, nothing there to change my remarks above.

Bugpack #4046 are 165 lbs at 1.550" and they say they can handle .630" lift. They don't specify if that's at coil bind or with some clearance remaining ... but if your installed height is only 1.450", those won't change much
Rob Penrose lists the CBPerformance #650 which is in the same ballpark, 160 lbs at 1.540" and .630" max, and they cost quite a bit more...not worth it if they only gain .010" clearance.
I can't find any other specs on the Engle 6602, they aren't listed in the Engle catalog (and they don't publish coil bind heights anyway) but perhaps Penrose could tell you.

http://www.scatvw.com/camshafts-acc/

[fabo]

Cb's are good springs though..never had any valve float with years of hillclimbs and supersprints.i think worth the extra $$$


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[Clatter]

FWIW,
In building Harley race and street motors, .060 from coil bind was used time and again.
.060 was the go-to number for several different builders, every one I ever talked to, actually..
In those circles, you either shimmed to .060, or you didn't.

Aren't the TCS series to be used with stock-ratio rockers?
Using ratio rockers, (Even just 1.25s) you might be asking quite a bit more from the springs..

IME, Scat springs are decent, but their life hasn't been as long as others..

[petew]

Yeah, so after lots of discussion and the like we've decided the following.
1. No ratio rockers. Stock rockers.
2. The head is being relieved a little to drop the spring pressures.
Hopefully that will do the trick. Thanks for your help people.

[Piledriver]

Berg sells +.100" retainers, reasonable price even.

[petew]

Cheers.